Similar to RRKPL's post in 2015, my resting heart rate appears to cycle very predictably between 53 and 58 bpm. It's not random - it's like a near-perfect sine wave. Since I'm male, it's not due to menstrual cycle as they talk about in medical literature. Cycle appears to be several days long, maybe a week. There's nothing I'm changing on my Fitbit use from day to day. The only thing I can think of is that I catch up a little on sleep on weekends and sleep times start and end later on weekends (although difference is not dramatic). Other than maybe sleep, what else might be causing this?
